In order to reinforce columns due to the increase of loads caused by the extension of a structure or strengthen a structure, to which no seismic design is applied, there is a method of reinforcing the outside of the column by means of steel jacketing, concrete jacketing or the like (Korean Patent No. 10-1568016 etc.).
In the steel jacketing method, an outer circumferential surface of an existing column formed of concrete is enclosed and fixed by a plurality of steel sheets by using fastening members or the like.
However, the steel jacketing method has a problem that since the steel sheet is vulnerable to fire or corrosion, the steel sheet needs to have additional fireproofing and rustproofing treatments. In addition, a separate structure is required to ensure the integrity between the steel sheet and the concrete.
Meanwhile, in the concrete jacketing method, an existing column is reinforced by increasing the cross-sectional area of the column by arranging reinforcing bars on the outside of the existing column, installing forms, and then pouring concrete.
The concrete jacketing method has advantages in that, unlike the steel jacketing method, there is no need for additional fireproofing and rustproofing treatments, it is also advantageous in ensuring the integrity with the existing concrete column, and the like.
However, it is difficult to prevent buckling of column main reinforcing bars due to the interference of the existing column or directly apply cross ties, which are installed for concrete confinement or the like. Accordingly, it is necessary to form a jacketed column in such a manner that a hole is punctured at a predetermined depth in the existing column and an anchor is installed so as to fix the cross tie, thereby decreasing constructability. In addition, there is a disadvantage in that it takes a long construction time due to a lot of field work.